The title says it all.. I got a garmin nuvi, a good car GPS. I love it. My only trouble: despite my best tries, the suction cup still tends to come off at the most inopportune moments, which can be very.. unsettling. I continue to drive, and listen only, but still, that is not good!
Any suggestions on how to make it work better? I tried clean the glass and the suction cup with windex and let it dry completely, I tried saliva

... What in blue blazes am I doing wrong?!
I noticed it happens with temperature changes a lot (between outside and inside - like I get in the car, it is freezing cold, I start and put on the heater - the suction cup jumps off after a few minutes. Same thing in summer ; lot less when the temperature is more reasonible).
As usual, if this isn't the good place or if I overlooked another similar thread, mods feel free to move /merge!